Cardiopulmany bypass heater cooler unit linked to outbreak of mycobacterium

[Julie Hunt]

Dear Colleagues

There was a paper published in July 2015 on a small number of patients who have been infected with Mycobacterium chimaera associated with heater-cooler units used during cardiac surgery. Our perfusionist also advised that an Australian HCF isolated non-tuberculous mycobacteria from the water of a cardiopulmonary bypass heater cooler unit recently, although they did not find transmission to patients. However, as the clinical manifestations associated with non-tuberculous mycobacteria are delayed it may take years for cases to manifest.

There is no direct contact between the water in the tanks of the heater cooler units and the patient. The water is pumped through a stainless steel tube, water flow on one side and blood on the other. The water heats or cools the stainless steel which in turn heats or cools the blood which heats or cools the patient. This allows reduction of the patients temperature to 15C and returns them back to 37C.

The water inside the tank is kept in motion by stirring devices and the authors of the paper write that this produces bubbles known to aerosolize. Alternatively, they propose that transmission may be due to droplets from tubes or connections could have reached the turbulent airflow produced by the fan of the heat exchanger in the lower part of the heater-cooler unit.

Some heater cooler units have a disinfection mode to 90C while others use various cleaning/disinfection chemicals. The manufacturers instructions indicate that water should be changed every 2 weeks to monthly depending on the type of unit used.

If your HCF provides services requiring cardiopulmonary bypass, can you please advise if action has been taken in view of the potential risk of non-tuberculous mycobacteria transmission to patients and if so what action your HCF has taken. i.e. changes to the schedule or method of cleaning and disinfection and/or water or air sampling during operation of the units.

Regards

Julie Hunt

Clinical Nurse Consultant
Infection Prevention & Control
Royal North Shore Hospital
Reserve Rd St Leonards 2065
Tel 02 99264339 or 99264490
Email: Julie.Hunt1@health.nsw.gov.au

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